A typical liquid crystal display (LCD) includes a liquid crystal panel and a backlight module. The backlight module generally includes a reflection sheet, a light source, a diffuser, and a brightness enhancement film. The light source can include one or more cold cathode fluorescent lamps, or one or more light-emitting diodes (LEDs). A backlight module using LEDs as a light source can include three different types of LEDs, which emit red, green, and blue light beams respectively. After mixing of the color light beams emitted by the red, green, and blue LEDs, a white surface light source can be achieved. The white surface light source illuminates the liquid crystal panel.
Referring to FIG. 6, a typical LCD 2 includes a liquid crystal panel 24, a backlight module 20 adjacent to the liquid crystal panel 24, and a frame 21. The backlight module 20 is configured to illuminate the liquid crystal panel 24.
The frame 21 includes a bottom 211 and four side walls 212. The four side walls 212 are perpendicularly connected with the bottom 211, thereby forming an accommodating space. The accommodating space accommodates the backlight module 20 and the liquid crystal panel 24.
The backlight module 20 includes a plurality of red, green, and blue LEDs 23, a reflective film 25, and a diffusing film 29. Each LED 23 includes a light-emitting portion 233, and a base 231 for supporting the light-emitting portion 233. The base 231 is located on the bottom 211 of the frame 21. The diffusing film 29 is adjacent to the liquid crystal panel 24. The reflective film 25 is adjacent to the bottom 211. The reflective film 25 includes a plurality of holes (251) corresponding to the plurality of LEDs 23. A light-mixing space 295 is defined between the reflective film 25 and the diffusing film 29.
The plurality of LEDs 23 emit red, green and blue light beams. Part of the light beams transmit directly to the diffusing film 29, and another part of the light beams transmit to the reflective film 25, and are reflected to the diffusing film 29. The red, green and blue light beams are mixed into white light beams in the light-mixing space 295.
However, if the light-mixing space 295 is small, the red, green and blue light beams may not be perfectly mixed. The mixed white light beams may appear a little yellow or blue, which reduces the color performance of the LCD 2. Therefore, the frame 21 is generally formed to be quite high (thick) in order to enlarge the light-mixing space 295 of the backlight module 20. The thick frame 21 increases a thickness of the LCD 2. This means the LCD 2 may be unsuitable for certain compact applications.
What is needed, therefore, is a backlight module that can overcome the above-described deficiencies.